A word's hold on time — when its meaning happens. In grammar, the marker of past, present, or coming.
Old French tens (time), from Latin tempus (time); a word's hold on time, marking when its meaning happens, is named for time itself rather than for anything strained or tight.
What pins a sentence's meaning to a moment rather than leaving it floating free of time. Grammar's own way of saying whether a thing already happened, is happening now, or has yet to.